Solvent extraction with a three-dimensional reticulated hollow-strut SiC foam microchannel reactor

Recently,there has been considerable interest in the use of microchannel reactors for hydrometallurgy of rare earths(REs).Here,a novel integrated microchannel reactor based on the hollow-strut SiC foam material is presented and demonstrated to extract Ce^(3+)and Pr^(3+)using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(P507)as the extractant.The typical three-dimensional reticulated structure of the hollow-strut SiC foam was characterized by scanning electron microscopy and X-ray micro computed tomography.Since the reactor’s structure plays a key role in fluid mixing and mass diffusion during the extraction process,the structure-performance relationship of the foam was studied by extraction experiments combined with numerical simulations.Using the foam with the optimal structure,the influence of the flow rate Q_(0) of the two liquid phases on the extraction efficiency η and overall volume mass transfer coefficient KLa was discussed.For both RE ions,with increasing Q_(0),η decreases while KLa increases.For the total flow rate of the two phases of 4 ml·min^(-1),the η values of Pr^(3+)and Ce^(3+)reached 98.7%and 97.0%,respectively.For the total flow rate of 36 ml·min^(-1) which was much higher than that of many other microchannel reactors reported in the literatures,the η values of Pr^(3+)and Ce^(3+)still reached 92.2%and 86.9%,respectively,and the KLa values of Pr^(3+)and Ce^(3+)were 0.198 and 0.161 s^(-1),respectively,similar to the high values reported for other microchannel reactors studied in previous work.These findings indicate that the hollow-strut SiC foam microchannel reactor is suitable for use in REs extraction.

Chaetarthria chenjuni Jia & Yang, sp. nov.(Coleoptera: Hydrophilidae), a new species from China and additional faunistic records

A new species of Chaetarthria Stephens,1835,is described from China,namely Chaetarthria chenjuni Jia&Yang,sp.nov.from Hainan,Guangdong and Guangxi Provinces,China.It is unique in the C.indica group by having the distinct punctures,as strong as those of puncture series,on the elytra.The broad median lobe of aedeagus has a round apex,which can be used to separate it easily from other known species occurring in the Oriental Region.

Hydrochlorination of Acetylene Using SiC Foam Supported Structured C/Au Catalysts

AuCl3 loaded structured catalysts were prepared on SiC foam supported with pre-coated activated carbon layers. The catalytic properties of the structured catalysts towards hydrochlorination of acetylene were tested in a fixed- bed reactor with the AuCl3 loaded on activated carbon pellets as a reference. For isopyknic catalysts, the structured catalyst with only one fifth of the Au amount as that was used on the reference catalyst exhibited even a little higher acetylene conversion and much better stability than the latter no matter what the gas hourly space velocities of acetylene were used. The results indicated that the more homogeneous distribution of AuCl3 particles and better heat transfer along the fixed-bed reactor originated from the low pressure drop and high thermal conductivity of the SiC foam supported structured catalysts might be able to account for their improved efficiency and stability. It is befieved that these novel structured C/Au catalysts can be potentially applied in VCM industrialization in view of their greatly reduced cost and much prolonged life.

A comparative study of Ni/Al_2O_3–SiC foam catalysts and powder catalysts for the liquid-phase hydrogenation of benzaldehyde

In this study, Al_2O_3-washcoated SiC(Al_2O_3–SiC) foams and Al_2O_3 powder were employed as the supports of a Ni catalyst for the liquid-phase hydrogenation of benzaldehyde. A series of Ni/Al_2O_3–SiC foam catalysts and Ni/Al_2O_3 powder catalysts with a Ni loading from 10 wt% to 37 wt% of the weight of Al_2O_3 were first prepared by a deposition–precipitation(DP) method. The catalytic activity and recyclability of both kinds of catalysts were then compared. Although it had a smaller accessible surface area with the reactant, the foam catalyst with a Ni loading of 16 wt% exhibited a slightly higher conversion of benzaldehyde after 6 h(of 99.3%) in comparison with the Ni/Al_2O_3 catalyst with identical Ni loading(conversion of 97.5%). When the Ni loading increased from 16 wt% to 37 wt%, the reaction rate obtained with the foam catalyst increased significantly from 0.108 to 0.204 mol L^(-1)h^(-1), whereas the reaction rate obtained with the powder catalyst increased from 0.106 to 0.123 mol L^(-1)h^(-1). Furthermore, the specific activity(moles of benzaldehyde consumed by 1 g min^(-1)of Ni) of the foam catalyst with a Ni loading above 30 wt% was superior to that of the powder catalyst because of its smaller Ni-particle size and higher mass-transfer rate. The foam catalyst displayed a high recyclability as a function of run times owing to the strong interaction between the Ni component and the Al_2O_3 coating. The conversion of benzaldehyde over the foam catalyst remained almost unchanged after being used 8 times. In comparison, a drop of 43% in the conversion of benzaldehyde with the powder catalyst was observed after being used 7 times due to the leaching of the Ni component.

Novel TiC/Ti Open Cellular Foams Prepared by a Modified Sponge-coating Method Using High Frequency Induction Heating Process

A new kind of open cellular foam material with three dimensionally interconnected TiC/Ti struts was prepared by a two-step sponge-coating and high frequency induction heating process. The microstructure, composition and compression strength of the prepared TiC/Ti foam materials were characterized. It was confirmed that the incorporation of Ti into TiC resulted in an inter-bonded Ti-TiC-Ti layered structure in the struts, which enhanced the plasticity of the composite foam materials.

Photocatalytic Activities of TiO_2 Coated on Different Semiconductive SiC Foam Supports

Different semiconductive SiC foam supports were prepared by varying the sintering temperature and atmosphere, and with or without alkaline solution treatment and high temperature oxidation following a macromolecule pyrogenation combined with reaction bonding method. Nano-TiO2 particles were immobilized onto these SiC foam supports by a composite sol-gel method. The phase, surface morphology, the type of conduction and the photocatalytic activity of the TiO2-SiC composite photocatalysts were studied. The TiO2 coated on p-type Si-free SiC support showed the highest photocatalytic efficiency in degradation of 4- aminobenzenesulfonic acid （4-ABS） in aqueous solution as compared to that coated on n-type SiC support and p-type SiC supports with residual Si or Si02 on the surface. The result showed that the TiO2 coatings immobilized on p-type semiconductive SiC foam supports exhibited obviously higher photocatalytic activity in comparison to that coated on n-type SiC foam support. The p-n heterojunctions formed between the p-type SiC supports and n-type TiO2 coatings might be able to account for the better charge separation and transfer as well as the photocatalytic activity of the TiO2-SiC composite photocatalyst.

Solvent extraction of Ce(Ⅲ) and Pr(Ⅲ) with P507 using SiC foam as a static mixer

Extraction reactor is a major research area of interest within the field of rare earths extraction and separation.SiC foam offers excellent material characteristics as well as three-dimensional(3-D) reticulated structure;however,very little research has been carried out on its application in extraction reactor so far.In this work,a static mixer reactor based on SiC foam was designed and demonstrated to extract and separate Ce(Ⅲ) and Pr(Ⅲ) from nitric acid media by using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(P507) as extractant.The structure-performance relationship between SiC foam and extraction performance was studied by experiment combined with computational fluid dynamics(CFD)simulation.The experiment data are in good agreement with the simulation results.Contrast experiment by using a Kenics mixer was carried out,and SiC foam shows better extraction and mass transfer performance.Using the optimal structural SiC foam(pore size D=2.3 mm,open porosity ε=85%,foam length L=80 mm),high extraction efficiency η(Pr(Ⅲ):94.6%,Ce(Ⅲ):88.5%) and separation factor β(2.27) between Ce(Ⅲ) and Pr(Ⅲ) is achieved at a high total throughput of 200 mL/min.Besides,overall volumetric mass transfer coefficient K_(L)a of Pr(Ⅲ) and Ce(Ⅲ) are 0.519 and 0.378 s^(−1) at the residence time τ of 3.6 s,respectively,which reach the high level of microchannel reactors and are better than conventional extractors and other static mixers.SiC foam is found to be applicable as a static mixer for efficient and high-throughput extraction and separation of rare earths.